I'm 99% sure that this is the case!
As for the UKCAT, I also think they don't know you did the extra time version until later on, when the universitys may ask you to provide proof of your dyslexia.
Seriously, its not worth worrying about! You get judged on your academic merits, UKCAT and PS, not on any disabilities or things like that. According the the Disability Act (1998 I think??) they are legally not allowed to discriminate against people with a disability, so the suggestion that they would use dyslexia as a screening tool is illegal! So stop stressing, do the extra time UKCAT if it will give you the best chance of performing to your potential for UKCAT, and check the UCAS box!!